Currently we are in 12.1.3 and we can customize our Configurator by writing own Java codes as per business need.
We are analyzing Oracle Cloud PAAS model and were going thru Oracle Configurator Cloud documentation and few Oracle provided quick tours like below -
One thing we are not clear, whether we can still customize above Cloud version of Configurator by writing our own JAVA in the same way we are doing now in 12.1.3
Oracle Cloud Configurator (R 13) Extensions needs to be written in the 'Groovy scripting language'. Refer 'http://groovy-lang.org/' for more details.
You can refer to the official documentation for the details of Groovy APIs provided to interact with model nodes at run time.